The present invention relates to efficient transfer of datalink frame or network packets in a “custom” network. The network is “custom” as all switches and end nodes need to create or process datalink frames or data packets of special formats.
The OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Most networking protocols do not implement all seven layers, but only a subset of layers. For example, TCP and IP protocol corresponds to layers 4 (TCP) and 3 (IP) respectively. Network packets contain protocol layer information corresponding to the packet. For example, a TCP/IP packet contains a header with both TCP and IP information corresponding to the packet.
The physical layer (layer 1) specifies how bits stream is created on a network medium and physical and electrical characteristics of the medium. The datalink layer (layer 2) specifies framing, addressing and frame level error detection. For outgoing packets to the network, the datalink layer receives network packets from networking layer (layer 3) and creates datalink frames by adding datalink (layer 2) protocol information and passes the frame to the physical layer. For incoming packets from network, datalink layer receives datalink frames from physical layer (layer 1), removes the datalink (layer 2) protocol information and passes network packet to the networking layer. The network layer (layer 3) specifies network address and protocols for end to end delivery of packets.
Network packets contain protocol layer information corresponding to the packet. FIG. 1A illustrates a network packet containing 01001 layer 1, 01002 layer 2, 01003 layer 3, 01004 layer 4 headers, 01005 Data and 01008 layer 1, 01007 layer 2, 01006 layer 3 trailers. FIG. 1B illustrates a network packet with 01011 layer 1, 01012 layer 2 (data link), 01013 layer 3 (networking) and 01014 layer 4 (transport) headers and 01017 layer 1 and 01016 layer 2 trailers and 01015 Data. For each layer, the corresponding header and trailer (if present) together contain all the protocol information required to send the packet/frame to the consumer of the data in a remote node.
For example, headers/trailers corresponding to a TCP/IP packet in a 10BaseT Ethernet LAN are:                i) Physical layer header contains Start-of-Stream Delimiter        ii) Data link layer header contains Preamble, Start-of-Frame Delimiter, Ethernet Addresses, Length/Type Field etc.        iii) IP header contains Version, Length, IP Address etc.        iv) TCP header contains Port Numbers, Window, Flags etc.        v) Datalink layer trailer contains 32 bit FCS        vi) Physical layer trailer contains End-of-Stream Delimiter.        
When parts of networks get congested and end nodes continue transmitting packets to congested parts of a networks, more and more switches can get congested. This can lead to switches dropping large number of packets, nodes retransmitting the dropped or lost packets and network slowing down.
U.S. Pat. No. 6,917,620 specifies a method and apparatus for a switch that separates the data portion and the header portion. This method has a disadvantage that overhead and logic for separating the data portion and the header portion and then combining the header portion and the data portion before transmission is required. This method also can not consolidate headers from more than one packet for transmission to the next node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.
According to claim (1)(c) of U.S. Pat. No. 5,140,582, the header portion of a packet is decoded prior to the receipt of full packet to determine the destination node. This invention can help with faster processing of the packet within a switch. This method can not consolidate headers from more than one packet for transmission to the next node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.
U.S. Pat. No. 6,032,190 specifies an apparatus and method of separating the header portion of an incoming packet and keeping the header portion in a set of registers and combining the header portion with the data portion before transmitting the packet. This method has a disadvantage that overhead and logic for separating the data portion and the header portion is required. This method can not consolidate headers from more than one packet for transmission to the next-node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.
U.S. Pat. No. 6,408,001 improves transport efficiency by identifying plurality of packets having common destination node, transmitting at least one control message, assigning label to these packets and removing part or all of header. This method has a disadvantage that switches need to identify messages with common destination node and additional logic to remove header and add label. This method can not delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.